Fuel burner ignitor



,Oct 8, 1968 A. P. sAHA 3,404,939 FUEL BURNER IGNITOR Filed Oct. 6, 1965i n {f/mssslkgffssms smX HHH mmf/Hummm mm l l l INVENTOR.

AATTO P. SAHA.

ATTORNEY.

Elsa United States Patent O 3,404,939 FUEL BURNER IGNITOR Aatto P. Saha,Jamesville, N.Y., assignor to Carrier Corporation, Syracuse, N.Y., acorporation of Delaware Filed Oct. 6, 1965, Ser. No. 493,444 2 Claims.(Cl. 431-263) This invention relates to an ignitor for use with adispersible fuel burner and, more particularly, to such an ignitor forproviding a highly stable pilot flame in the form of an outwardly'diverging free spiral vortex.

Various types of ignitors which provide a pilot flame often requirecritical adjustment, such as exact fuel-air ratio and pressure, in orderto function properly, and are often subject to blowout of the iiame.

It is a primary object of this invention to provide a new and improvedignitor for igniting a main flame of a dispersible fuel burner. Arelated object is provision of such an ignitor which provides a highlystable pilot flame in the form of an outwardly diverging free spiralvortex. A related object is provision of such a flame which issubstantially unaifected by the variations in the fuel-air ratio orpressure of the fuel or air, and by the main fuel being ignited and theresultant main fiame.

Additional objects and advantages of the invention will be apparent fromthe following drawing in which:

FIGURE 1 is a fragmentary, longitudinal sectional view of a dispersiblefuel burner, including a preferred embodiment of an ignitor, mounted onan end of a combustion chamber; and

FIGURE 2 is an enlarged, transverse sectional view of the ignitor takengenerally along the line II-II in FIG- URE l.

In the embodiment illustrated in the drawing, a combustion chamber 11includes a cylindrical side wall 12 and an end wall 13. A dispersiblefuel burner 14 includes a main supply line 15 to a dispersible fuel mainnozzle 16 illustrated as mounted on and opening through the longitudinalcenter of the end wall 13 for projecting a combustible spray 17 of gasor oil into the combustion chamber 11 to -burn and provide a main burnerllame.

An ignitor 18 for igniting the spray 17 from the main nozzle 16includes/a tube 19 having one end suitably secured to and openingthrough the combustion chamber end wall 13 to provide an ignitor nozzleorifice 20 for projecting a free spiral vortex pilot flame 21 divergingoutwardly from the ignitor nozzle orifice 20 into the spray 17 from themain nozzle 16. The ignitor 18 includes a `body 22 and a vortex carryingcombustion passage 23, illustrated as a cylindrical passage extendingfrom the ignitor nozzle 20 at one end to an opposite rear end 24 of thebody 22. The ignitor body 22 is mounted on the combustion chamber endwall 13 by means of the tube 19 which has a rear end opposite the nozzleorifice 20 telescopically received in an enlarged socket about the frontend of the passage 23 in the body 22 and detachably secured lby a setscrew 25. The interior diameter of the tube 19 is substantially the sameas the diameter of the portion of the combustion passage 23 in the body22.

Vortex forming means is illustrated in the form of a plurality of airpassages 26 (FIGURE 2) extending through the body 22 and openingtangentially through ports 27 into the rear end 24 of the combustionpassage 23 and communicating with an air plenum 28 connected with an airsupply line 29 for passing air through the air passages26 to form a freespirtal vortex of combustion air 30 traveling axially slowly through thepassage 23 to the nozzle orifice 20 with an axial velocity less than thepilot flame propagation rate, thus substantially preventing popping ofthe pilot flame 21. The Vortex 30 of combustion air includes an annularportion 31 rotating relatively ICC rapidly about a relativelysubstantially slower rotating core 32.

A pilot gas supply tube 33 extends through the air plenum 28 and througha bore in the rear end 24 of the ignitor body 22 to an open enddischarge portion 34 generally coaxial with the combustion passage 23land slightly downstream of the vortex forming ports 27 Ifor projecting ajet of combustible gas 35 axially through the vortex core 32. Ifdesired, air ports 36 communicating with the air plenum 28 may beprovided in the gas tube 33 to mix a small amount of air with the gas inthe tube 33 before formation of a combustible mixture of the vortex airand the gas.

Means for igniting the resultant combustible mixture of vortex air andgas in the combustion passage 23 includes a spark plug 37 threadedlymounted in a nipple 38 suitably secured to the body 22, and openingthrough a port 39 in the body so that the spark plug electrodes 40 arepositioned for igniting the combustible mixture of air formed at theinner face 41 of the rapidly rotating annular portion 31 of the vortex30. The combustion passage 23 is substantially unobstructed so that theaxial velocity of the air and gas moving through this passage issubstantially constant below the flame propagation rate, and theresultant flame 21 extends through the combustion passage 23 fromsubstantially the discharge end 34 of the gas supply tube 33 to andthrough the ignitor nozzle orifice 20.

As the pilot llame 21 emerges from the orifice 20, it diverges outwardlybecause of the centrifugal force of the various gases emitted from theorifice, to form a hollow conical pattern including combustible mixtureand flame which penetrates and ignites the spray of combustible mixture17 from the main nozzle 16. Satisfactory results may be obtained with acombustion passage diameter of 1% and length from tube open end 34 to2", four equally spaced air passages 26 of 1A diameter, a 1/2" diametergas supply tube 35, plenum airpressure drop and natural gas supplypressure drop across the ignitor of 1 water.

Should a quantity of gas in excess of the optimum fuel-air ratio beprojected through the gas tube 33 into the vortexcore 32, the excessgas, as 42, is projected through the eye of the conical pilot flame 21and into the combustion chamber 11 to burn" therein with the arne fromthe main nozzle 16. Similarly, should an excess quantity of combustionair bey provided in the vortex 30, the excess air, as 43, will spilloutwardly about the conical flame 21 and combine with the ame from themain nozzle` '16. In the event of actual blowout of the conical pilotflame 20, as by the combustible mixture or llame from the main nozzle16, for example, the combustible mixture burning a substantial distancewithin the combustion passage 23 again immediately ignites the conicalportion of the pilot flame, so that, in effect, the pilot flame does notblow out. Only a small portion of the gas and air available to form apilot combustible mixture is burned within the ignitor body, leavingmost of the pilot combustible mixture to establish a relatively largepilot flame in the combustion chamber 11. Spreading of the conical pilotflame toward the combustible mixture from the main nozzle 16, makespositioning of the ignitor less critical relative to the main burnernozzle 16.

While a preferred embodiment of the invention has been described andillustrated, it should be understood that the invention is not limitedthereto but may be otherwise embodied within the scope of the followingclaims.

I claim:

1. In an igniter for use with a dispersible fuel burner to provide apilot flame for igniting a main combustible mixture, the combination ofa tube having one end opening through a combustion wall chamber of theburner to provide a nozzle orifice for projecting a free spiral Ivortexame diverging outwardly from the nozzle orifice, a body forming a vortexcarrying combustion passage extending from the nozzle orice to theopposite rear end of the body, said body being mounted on said tube,vortex forming means including a plurality of air passages extendingthrough the body and opening tangentially into the rear end of thecombustion passage to form a free spiral vortex of combustion airadapted to travel axially through the passage to the nozzle orifice withan axial velocity less than the pilot ame propagation rate, the vortexincluding an annular portion rotating relatively rapidly about arelatively slower rotating core, a pilot gas supply tube extendinggenerally coaxial with the combustion passage and slightly downstream ofthe openings of said air passages for projecting a jet of cornbustiblegas axially through the vortex core, and igniter means for igniting thecombustible mixture in said combustion 4passage to provide a pilot ame,said tube nozzle orifice discharging the pilot flame from saidcombustion passage in an outwardly diverging hollow conical pattern toignite the main combustible mixture.

2. An igniter according to claim 1 in which a plurality of air ports areprovided in the gas supply tube.

References Cited UNITED STATES PATENTS 1,369,602 2/1921 Amsler 158-109XR 2,117,356 5/1938 Perry 158-991 X 2,723,659 11/1955 Young et al158-991 X 2,876,832 3/1959 Peters 158-115 2,952,307 9/1960 Schram et al158-110 X 3,002,819 10/1961 Brace et al 239-405 X 3,265,113 8/1966Thurley et al 158-109 3,273,623 9/1966` Nesbitt 15S-991 X FREDERICK L.MA'ITESON, JR., Primary Examiner.

H. B. RAMEY, Assistant Examiner.

1. IN AN IGNITER FOR USE WITH A DISPERSIBLE FUEL BURNER TO PROVIDE APILOT FLAME FOR IGNITING A MAIN COMBUSTIBLE MIXTURE, THE COMBINATION OFA TUBE HAVING ONE END OPENING THROUGH A COMBUSTION WALL CHAMBER OF THEBURNER TO PROVIDE A NOZZLE ORIFICE FOR PROJECTING THE FREE SPIRAL VORTEXFLAME DIVERGING OUTWARDLY FROM THE NOZZLE ORIFICE, A BODY FORMING AVORTEX CARRYING COMBUSTION PASSAGE EXTENDING FROM THE NOZZLE ORIFICE TOTHE OPPOSITE REAR END OF THE BODY, SAID BODY BEING MOUNTED ON SAID TUBE,VORTEX FORMING MEANS INCLUDING A PLURALITY OF AIR PASSAGES EXTENDINGTHROUGH THE BODY AND OPENING TANGENTIALLY INTO THE REAR END OF THECOMBUSTION PASSAGE TO FORM A FREE SPIRAL VORTEX OF COMBUSTION AIRADAPTED TO TRAVEL AXIALLY THROUGH THE PASSAGE TO THE NOZZLE ORIFICE WITHAN AXIAL VELOCITY LESS THAN THE PILOT FLAME PROPAGATION RATE,